Method for processing data associated with session management and mobility management

ABSTRACT

A user equipment (UE) in a communication system, and a method thereof. The method includes establishing; by a user equipment (UE), a first data connection associated with an access point name (APN); receiving, by the UE, a session management back-off time value when a request of a bearer resource modification or a bearer resource allocation for the established first data connection is rejected; starting, by the UE, a session management back-off timer according to the session management back-off time value, the session management back-off timer being associated with the established first data connection; if the UE receives a deactivate bearer context request message indicating that reactivation is requested, stopping the session management back-off timer if the session management back-off timer is running; and establishing, by the UE, a second data connection associated with the APN after stopping the session management back-off timer.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of co-pending U.S. patent applicationSer. No. 13/458,427 filed Apr. 27, 2012, which claims priority to U.S.Provisional Application No. 61/481,082 filed on Apr. 29, 2011, and PCTInternational Application No. PCT/KR2012/003274 filed on Apr. 27, 2012.The entire contents of all of the above applications are herebyincorporated by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The technical features of this document relate to wirelesscommunications, and more particularly, to a method for processing dataassociated with bearer resources in a wireless network.

2. Discussion of the Related Art

The Third Generation Partnership Project (3GPP) Long Term Evolution(LTE) which is a set of enhancements to the Universal MobileTelecommunications System (UMTS) is introduced as 3GPP Release 8. The3GPP LTE uses orthogonal frequency division multiple access (OFDMA) fora downlink, and uses single carrier frequency division multiple access(SC-FDMA) for an uplink, and adopts multiple input multiple output(MIMO) with up to four antennas. In recent years, there is an ongoingdiscussion on 3GPP LTE-Advanced (LTE-A), which is a major enhancement tothe 3GPP LTE.

The 3GPP LTE system provides session management and mobility managementprocedures to alleviate the congestion of the network. When performingthe session management or mobility management, the network may provideback-off timers to control further signaling from the UE.

SUMMARY OF THE INVENTION

The technical features of this document provide a method and wirelessapparatus for processing data associated with hearer resources, sessionmanagement, and/or mobility management in a wireless networktransmitting a radio signal based on a number of orthogonal frequencydivision multiplexing (OFDM) symbols. The technical features can be usedto improve the performance of the wireless network, and/or to solve theproblem caused by the abnormal situation.

In one aspect, the method comprises transmitting, by a user equipment(UE), a first packet data network connectivity request message to amobility management entity (MME) for establishing a packet data networkconnection; receiving, by the UE, a radio resource control (RRC)connection reconfiguration message including a packet data networkconnectivity accept message which is transmitted from the MME;receiving, by the UE, a session management back-off time value from theMME when a request of bearer resource modification or bearer resourceallocation for the established packet data network connection isrejected by the MME; starting, by the UE, a session management back-offtimer according to the session management back-off time value, thesession management back-off timer being associated with the establishedpacket data network connection; receiving, by the UE, a deactivatebearer context request message, from the MME, including a cause codeindicating that reactivation is requested and stopping the sessionmanagement back-off timer if the session management back-off time srunning; and transmitting, by the UE, a second packet data networkconnectivity request message to the MME after stopping the sessionmanagement back-off timer.

A value of the cause code may be set to ‘39’.

The session management back-off time value is included in a bearerresource modification reject message which is transmitted from the MME,and the UE does not transmit an additional request for the bearerresource modification while the session management back-off timer isrunning.

The bearer resource modification reject message includes a cause valuewhich is set to ‘26’, which indicates ‘insufficient resources’.

The session management back-off time value is included in a bearerresource allocation reject message which is transmitted from the MME,and the UE does not transmit an additional request for the bearerresource allocation while the session management back-off timer isrunning.

The bearer resource allocation reject message includes a cause valuewhich is set to ‘26’, which indicates ‘insufficient resources’.

The first packet data network connectivity request message and thesecond packet data network connectivity request message are associatedwith a same access point name (APN).

The deactivate bearer context request message identifies a bearercontext to be deactivated by the UE, and the second packet data networkconnectivity request message is associated with a same access point name(APN) as the deactivated bearer context.

The cause code included in the deactivate bearer context request messageindicates that reactivation of a packet data network connectivity isrequested for a same access point name (APN) as a bearer context whichis deactivated by the deactivate bearer context request message.

In another aspect, a user equipment (UE) is further provided. Thecomprises a radio frequency (RF) unit configured for: transmitting afirst packet data network connectivity request message to a mobilitymanagement entity (MME) for establishing a packet data networkconnection; receiving a radio resource control (RRC) connectionreconfiguration message including a packet data network connectivityaccept message which is transmitted from the MME; receiving a sessionmanagement back-off time value from the MME when a request of bearerresource modification or bearer resource allocation for the establishedpacket data network connection is rejected by the MME; starting asession management back-off timer according to the session managementback-off time value, the session management back-off timer beingassociated with the established packet data network connection;receiving a deactivate bearer context request message, from the MME,including a cause code indicating that reactivation is requested andstopping the session management back-off timer if the session managementback-off timer is running; and transmitting a second packet data networkconnectivity request message to the MME after stopping the sessionmanagement back-off timer.

In another aspect, a method of communicating data in a wirelesscommunication system including a first type network communicating basedon a number of orthogonal frequency division multiplexing (OFDM)symbols, a second type network which is different from the first typenetwork, and a user equipment (UE) which is communicating with at leastone of the first type network and the second type network, the methodperformed by the UE which moves between a coverage of the first typenetwork and a coverage of the second type network is further provided.The method includes receiving a UE location registration accept messageindicating that an idle mode signaling reduction (ISR) function isenabled; transmitting a first control message to activate or modify apacket data protocol (PDP) context to the second type network; receivinga second control message including an mobility management back-off timevalue; staring an mobility management back-off timer based on themobility management back-off time value; receiving a paging messagewhile the mobility management back-off timer is running, wherein thepaging message is transmitted from the first type network by using asystem architecture evolution temporary mobile subscriber identity(S-TMSI); and transmitting, in response to the paging message, a firsttracking area update (TAU) request message to the first type network,wherein the UE's temporary identity (TIN) used in next update indicatesa packet temporary mobile subscriber identity (P-TMSI).

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a view illustrating an Evolved Packet System which isassociated with the Long Term Evolution (LTE) system.

FIG. 2 is a view illustrating an overall architecture of the E-UTRAN towhich the following technical features are applied.

FIG. 3 is a view illustrating EPS bearers crossing multiple interfaces.

FIG. 4 is a flowchart illustrating a method of handling data fornetwork-ordered PDN connection re-activation during the SM timerrunning.

FIG. 5 is a flowchart illustrating a technical problem which may occurwhen the service request procedure is performed.

FIG. 6 is a flowchart illustrating a method of communicating data in awireless communication system including 2G/3G and LTE.

FIG. 7 is a block diagram showing a wireless apparatus to implementtechnical features of this description.

DETAILED DESCRIPTION OF THE INVENTION

The technology described below can be used in various wirelesscommunication systems such as code division multiple access (CDMA), afrequency division multiple access (FDMA), time division multiple access(TDMA), orthogonal frequency division multiple access (OFDMA), singlecarrier frequency division multiple access (SC-FDMA), etc. The CDMA canbe implemented with a radio technology such as universal terrestrialradio access (UTRA) or CDMA-2000. The OFDMA can be implemented with aradio technology such as institute of electrical and electronicsengineers (IEEE) 802.11 (Wi-Fi), IEEE 802.16 (WiMAX), IEEE 802-20,evolved UTRA (E-UTRA), etc. The UTRA is a part of a universal mobiletelecommunication system (UMTS). The 3^(rd) generation partnershipproject (3GPP) long term evolution (LTE) is a part of an evolved UMTS(E-UMTS) using the E-UTRA. The 3GPP LTE uses the OFDMA in the downlinkand uses the SC-FDMA in the uplink. For clarity of explanation, thefollowing description will focus on the 3GPP LTE (or the 3GPP LTE-A).However, the technical features of this description are not limitedthereto.

FIG. 1 is a view illustrating an Evolved Packet System which isassociated with the Long Term Evolution (LTE) system. The LTE systemaims to provide seamless Internet Protocol (IP) connectivity between auser equipment (UE) and a pack data network (PDN), without anydisruption to the end user's application during mobility. While the LTEsystem encompasses the evolution of the radio access through an E-UTRAN(Evolved Universal Terrestrial Radio Access Network) which defines aradio protocol architecture between a user equipment and a base station,it is accompanied by an evolution of the non-radio aspects under theterm ‘System Architecture Evolution’ (SAE) which includes an EvolvedPacket Core (EPC) network. The LTE and SAE comprise the Evolved PacketSystem (EPS).

The EPS uses the concept of “EPS bearers” to route IP traffic from agateway in the PDN to the UE. A bearer is an IP packet flow with aspecific Quality of Service (QoS) between the gateway and the UE. TheE-UTRAN and EPC together set up and release the bearers as required byapplications.

The EPC, which is also referred to as the core network (CN), controlsthe LTE and manages establishment of the bearers. As depicted in FIG. 1,the node (logical or physical) of the EPC in the SAE includes a MobilityManagement Entity (MME) 10, a PDN gateway (PDN-GW or P-GW) 30, a ServingGateway (S-GW) 20, a Policy and Charging Rules Function (PCRF) 40, aHome subscriber Server (HSS) 50, etc.

The MME 10 is the control node which processes the signaling between theUE and the CN. The protocols running between the UE and the CN are knownas the Non-Access Stratum (NAS) protocols. Examples of functionssupported by the MME 10 includes functions related to bearer management,which includes the establishment, maintenance and release of the bearersand is handled by the session management layer in the NAS protocol, andfunctions related to connection management, which includes theestablishment of the connection and security between the network and UE,and is handled by the connection or mobility management layer in the NASprotocol layer.

The S-GW 20 serves as the local mobility anchor for the data bearerswhen the LT moves between eNodeBs. All user IP packets are transferredthrough the S-GW 20. The S-GW 20 also retains information about thebearers when the UE is in an idle state (known as ECM-IDLE) andtemporarily buffers downlink data while the MME initiates paging of theUE to re-establish the bearers. Further, it also serves as the mobilityanchor for inter-working with other 3GPP technologies such as GPRS(General Packet Radio Service) and UMTS (Universal MobileTelecommunications System).

The P-GW 30 serves to perform IP address allocation tier the UE, as wellas QoS enforcement and flow-based charging according to rules from thePCRF 40. The P-GW 30 performs QoS enforcement for Guaranteed Bit Rate(GBR) bearers. It also serves as the mobility anchor for inter-workingwith non-3GPP technologies such as CDMA2000 and WiMAX networks.

The PCRF 40 serves to perform policy control decision-making, as well asfor controlling the flow-based charging functionalities.

The HSS 50, which is also referred to as a Home Location Register (HLR),contains users' SAE subscription data such as the EPS-subscribed QoSprofile and any access restrictions for roaming. Further, it also holdsinformation about the PDNs to which the user can connect. This can be inthe form of an Access Point Name (APN), which is a label according toDNS (Domain Name system) naming conventions describing the access pointto the PDN, or a PDN Address which indicates subscribed IP addresses.

Between the EPS network elements shown in FIG. 1, various interfacessuch as an S1-U, S1-MME, S5/S8, S11, S6a, Gx, Rx and SGi are defined.

FIG. 2 is a view illustrating an overall architecture of the E-UTRANtowhich the following technical features are applied.

The E-UTRAN includes at least one eNB (evolved-Node B) 200 providing auser plane and a control plane towards a user equipment (UE) 210. The UEcan be fixed or mobile and can be referred to as another terminology,such as a MS (Mobile Station), a UT (User Terminal), an SS (SubscriberStation), an MT(mobile terminal), a wireless device, or the like. TheeNB 200 may be a fixed station that communicates with the UE 100 and canbe referred to as another terminology, such as a base station (BS), a NB(NodeB), a BTS (Base Transceiver System), an access point, or the like.

The protocols running between the eNBs 200 and the UE 210 are known asthe Access Stratum (AS) protocols.

The BSs (or eNBs) 200 are interconnected with each other by means of anX2 interface. The BSs 200 are also connected by means of the SIinterface to the aforementioned EPC (Evolved Packet Core) elements, morespecifically to the Mobility Management Entity (MME) by means of the SI-MME and to the Serving Gateway (S-GW) by means of the S1-U.

The E-TURAN architecture depicted in FIG. 2 may further comprise a Homeevolved Node B (HleNB) 220 and an HeNB GW (HeNB gateway) 230.

The HeNB 220 is fundamentally similar to a typical eNB, but it can besimple devices typically installed by end users themselves. The HeNB 220is also referred to as an HNB (home NB), a femto cell, a home cellularbase station, etc, The HeNB 220 behaves like a cellular network withrespect to communication devices, which can use their regular cellularnetwork radio interface to communicate with them, and connects to acellular network operator's core network through the alternate networkaccess, such as Internet access via fiber, IDSL or cable subscriptions.In general, the HeNB 220 has a low radio transmission output powercompared to the BS owned by mobile communication service providers.Therefore, the service coverage provided by the HeNB 220 is typicallysmaller than the service coverage provided by the eNB 200. Due to suchcharacteristics, the cell provided by the HeNB 220 is classified as afemto cell in contrast to a macro cell provided by the eNB 200 from astandpoint of the service coverage.

Hereinafter, the concept of an APN (Access Point Name) will beexplained.

The APN is the name of an access point previously defined within anetwork to find a P-GW when a requested service is passed through theP-GW to access a network. The APN is provided to the UE, and the IJEdetermines a suitable P-GW for data transmission and reception based onthe APN.

The APN can be a configurable network identifier used by a mobile devicewhen connecting to a carrier. The carrier will then examine thisidentifier to determine what type of network connection should becreated, for example: what IP addresses should be assigned to thewireless device, what security methods should be used, and how/or if, itshould be connected to some private customer network. More specifically,the APN identifies an IP Packet Data Network (PDN), that a mobile datauser wants to communicate with. In addition to identifying the PDN, theAPN may also be used to define the type of service. The APN is used invarious access networks such as a general packet radio service (GPRS)and an evolved packet core (EPC).

Hereinafter, the concept of an EPS bearer will be explained.

The EPS (Evolved Packet System) uses the concept of EPS bearers to routeIP traffic from a gateway in the PDN (pack data network) to the LTE. TheEPS bearer is an IP packet flow with a Quality of Service (QoS) betweenthe gateway and the UE. The E-UTRAN and EPC (Evolved Packet Core)together set up and release EPS bearers as required by applications.

The EPS bearer is typically associated with the QoS. Multiple bearerscan be established for a user in order to provide different QoS streamsor connectivity to different PDNs. For example, a user might be engagedin a voice (e.g., VoIP) call while at the same time performing webbrowsing or File Transfer Protocol (FTP) download. A VoIP bearer wouldprovide the necessary QoS for the voice call, while a best-effort bearerwould be suitable for the web browsing or FTP session.

Broadly, EPS bearers can be classified into two categories based on thenature of the QoS they provide. The two categories are MinimumGuaranteed Bit Rate (GBR) bearers and Non-GBR bearers. The GBR bearershave an associated GBR value for which dedicated transmission resourcesare permanently allocated at bearer establishment/modification. Bitrates higher than the GBR may be allowed for a GBR bearer if resourcesare available. On the other hand, the non-GBR bearers do not guaranteeany particular bit rate. For these bearers, no bandwidth resources areallocated permanently to the bearer.

Further, EPS bearers can be classified in a different manner. Inparticular, the EPS bearers can be classified into a default bearer anda dedicated bearer. The default bearer is an EPS bearer which is firstestablished for a new PDN connection, and remains established throughoutthe lifetime of the PDN connection. The default bearer gets establishedwith every new PDN connection. Namely, when the UE connects to the P-GWby means of a procedure called “Initial Attach,” a new or default beareris created and its context remains established throughout the lifetimeof that PDN connection. The UE can be attached to more than one P-GW,and thus the UE can have More than one default bearer. The default EPSbearer is a non-GBR bearer and associated with a best effort QoS,wherein the best effort QoS is the lowest of all QoS traffic classes.Bearers which are not created at the initial attach procedure can bereferred to as dedicated bearers. The dedicated bearer is an EPS bearerthat is associated with uplink packet filters in the UE and downlinkpacket filters in the PDN GW where the filters only match certainpackets.

Hereinafter, the relationship of the EPS bearer and lower ayer bearerssuch as S1, S5/S8, radio bearers and E-RAB will be explained.

The EPS bearer has to cross multiple interfaces as shown in FIG. 3—theS5/S8 interface from the P-GW to the S-GW, the SI interface from theS-GW to the eNodeB, and the radio interface (also known as the LTE-Uuinterface) from the eNodeB to the UE. Across each interface, the EPSbearer is mapped onto a lower layer hearer, each with its own beareridentity. Each node keeps track of the binding between the bearer IDsacross its different interfaces.

An S5/S8 bearer transports the packets of the EPS bearer between theP-GW and the S-GW. The S-GW stores a one-to-one mapping between an Sibearer and an S5/S8 bearer. Each bearer is identified by the GTP (GPRSTunneling Protocol) based Tunnel Endpoint ID (also known as a TEID)across both interfaces.

An S5/S8 bearer transports the packets of an EPS bearer between the S-GWand the eNodeB. A radio bearer (also known as a radio data bearer)transports the packets of an EPS bearer between the UP and the eNodeB.Each bearer is identified by the GTP (GPRS Tunneling Protocol) tunnelendpoint ID (also known as a TEID or a GTP TEID) across both interfaces.

Further, the concept of the E-RAB (E-UTRAN Radio Access Bearer) may beused. An E-RAB transports the packets of an EPS hearer between the UEand the EPC (GPRS Tunneling Protocol), more specifically to the S-GWthrough eNB. When an E-RAB exists, there is a one-to-one mapping betweenthis E-RAB and an EPS bearer.

IP packets mapped to the same EPS bearer receive the same bearer-levelpacket forwarding treatment (e.g., scheduling policy, queue managementpolicy, rate shaping or RLC configuration). Providing differentbearer-level QoS thus requires that a separate EPS bearer is establishedfor each QoS flow, and user IP packets must be filtered into thedifferent EPS bearers.

Hereinafter, the concept of mobility management (MM) and a mobilitymanagement (MM) back-off timer is explained in detail. All UE-relatedinformation in the access network can be released during periods of datainactivity. This state can be referred to as EPS Connection ManagementIDLE (ECM-IDLE). The MME retains the UE context and the informationabout the established bearers during the idle periods.

To allow the network to contact a UE in the ECM-IDLE, the UE updates thenetwork as to its new location whenever it moves out of its currentTracking Area (TA). This procedure is called a ‘Tracking Area Update’,and a similar procedure is also defined in a universal terrestrial radioaccess network (UTRAN) or GSM EDGE Radio Access Network (GERAN) systemand is called a ‘Routing Area Update’. The MME serves to keep track ofthe user location while the UE is in the ECM-IDLE state.

When there is a need to deliver downlink data to the UE in the ECM-IDLEstate, the MME transmits a paging message to all base stations (i.e.,eNodeBs) in UE registered tracking area(s) (TA). Thereafter, eNBs startto page the UE over the radio interface. On receipt of a paging message,the UE performs a certain procedure which results in changing the UE toECM.-CONNECTED state. This procedure is called a ‘Service RequestProcedure’. UE-related information is thereby created in the E-UTRAN,and the bearers are re-established. Tie MME is responsible for there-establishment of the radio bearers and updating the UE context in theeNodeB.

When the above-explained mobility management (MM) is applied, a mobilitymanagement (MM) back-off timer can be further used. Upon receipt of atime value associated with the MM back-off timer, the UE may activatethe MM back-off timer according to the time value given by the network.Under the current 3GPP specification, while the MM back-off timer isrunning, UE is prohibited from performing the Tracking Area Update orRouting Area Update to the network. However, even when the MM back-offtimer is running, the UE can receive page message and be thereby paged,if the network has downlink data for the UE. As explained above, whenthe UE responding the page message, the Service Request Procedure isrequired under the current 3GPP specification.

Hereinafter, the concept of session management (SM) and a sessionmanagement (SM) back-off timer is explained in detail. The sessionmanagement (SM) is related to session management (SM) signaling whichcan be used for establishing PDN connectivity, allocating an additionalbearer or modifying a QoS of a certain bearer. For example, when the newservice (e.g., vow service is initiated, the UE may request the networkto allocate a new bearer by using the SM signaling. Further, the UE mayrequest to change a QoS of a certain bearer by using the SM signaling.The SM signaling can be initiated by EPS Session Management (ESM)requests from the UE (e.g., PDN Connectivity, Bearer ResourceAllocation, or Bearer Resource Modification Requests).

Under the current 3GPP specification, APN-based Session Management (SM)congestion control can be applied. In particular, the MME may reject theEPS Session Management (ESM) requests from the UP with a certainback-off timer when ESM congestion associated with the APN is detected.The above-mentioned timer can be referred to as a ‘Session Management(SM) back-off timer’. In the current specification, the SM back-off timecan be referred to as another terminology such as T3396 value, etc.

The MME may store a Session Management back-off time (or SM back-offtime value) when congestion control is active for an APN. The MME mayimmediately reject any subsequent request from the UE targeting to theAPN before the stored SM back-off timer is expired.

The SM back-off time (or time value) is transmitted from the MME to theUE when the network (e.g., MME) rejects the EPS Session Management (ESM)requests. For example, the SM back-off time value can be transmitted tothe UP when a request for bearer resource modification or bearerresource allocation is rejected by the MME. In particular, the SMback-off time value may be transmitted to the UP via a BEARER RESOURCEALLOCATION REJECT message and/or BEARER RESOURCE MODIFICATION REJECTmessage.

Upon reception of the SM back-off time value in the EPS SessionManagement reject message, the UE activates an SM back-off timeraccording to the received SM back-off time value. In particular, if APNis provided in the rejected EPS Session Management Request message, theUE may not initiate any Session Management procedures for the congestedAPN (e.g., sending PDN CONNECTIVITY REQUEST, BEARER RESOURCEMODIFICATION REQUEST or BEARER RESOURCE ALLOCATION REQUEST) except forreleasing the PDN connection (e.g. sending PDN Disconnection Request).The UE may initiate Session Management procedures for other APNs. If APNis not provided in the rejected EPS Session Management Request message,the UE may not initiate any Session Management requests without APN.Further, the UE may initiate Session Management procedures for specificAPN. The UE can support a separate SM back-off timer for every APN thatthe UE may activate.

The technical features in this description comprise a number ofembodiments related to mobility and session management. Hereinafter, thefirst embodiment which is related to network-ordered re-attach or PDNconnection reactivation while the MM or SM timer is running is explainedin detail.

As mentioned above, the UE may receive from the MME an SM back-off timevalue which is associated with an established PDN connection, when thenetwork has previously rejected bearer allocation or modificationrequest for the already established PDN connection. Namely, the SMback-off time value can be included .in BEARER RESOURCE ALLOCATIONREJECT message and/or BEARER RESOURCE MODIFICATION REJECT message.Further, under the current 3GPP specification, when the networkpreviously rejected MM signaling form UE, the UE is not allow to performmobility management (MM) procedures while the MM back-off timer isrunning.

In sum, under the current 3GPP specification, the UE is not allowed torequest the activation, allocation or modification of a bearer while theSM back-off timer is running. Further, under the current specification,the UE is not allowed to re-attach to the network while the MM back-offtimer is running.

However, there may occur an abnormal situation where the networkrequests re-establishment of a PDN connection or re-attachment to thenetwork while the SM/MM back-off timers are running. For example, acongested network may want to use Selected IP Traffic Offload (SIPTO),which allows data traffic to flow to and from an alternative gatewaybypassing the existing congested gateways in the operator's core networkin order to alleviate such congestion. in particular, the network maysend a DEACTIVATE EPS BEARER CONTEXT REQUEST message with an ESM causecode ‘39’ indicating ‘reactivation requested’, or a DETACH REQUESTmessage with a detach type indicating ‘re-attach required’. Uponreceiving such messages, the UE performs PDN connection deactivation ordetach. However, once the deactivation or detach is performed, the UEcannot signal the network for re-establishment or re-attachment, sinceit is prohibited while the SM/MM back-off timers are running.

In order to resolve such problems, the following description providestechnical features of for network-ordered PDN connection re-activationor re-reattachment.

FIG. 4 is a flowchart illustrating a method of handling data fornetwork-ordered PDN connection re-activation during the SM timerrunning. According to an example of FIG. 4, the UE stops at least the SMback-off timer, if running, of affected PDN connection(s) afterreceiving the DEACTIVATE EPS BEARER CONTEXT REQUEST message with an ESMcause code ‘#39’ indicating ‘reactivation requested’.

In step S301, to establish a PDN connection, the UE transmits a PDNconnection request message (i.e., PDN Connectivity Request) to the MMEvia the eNB. The PDN Connectivity Request includes information on an APN(Access Point Name), a PDN Type, Protocol Configuration Options, aRequest Type, or the like. The PDN type indicates the requested IPversion (IPv4, iPv4v6, IPv6). The Protocol Configuration Options (PCOs)are used to transfer parameters between the UE and the PDN GW, and aresent transparently through the MME and the Serving GW. The Request Typeindicates types (e.g., emergency, initial request, handover) ofconnections.

In step S302, the MME allocates a bearer ID and transmits a sessionrequest message (i.e., the Create Session Request) to the S-GW.

In steps S303 to S805, a Create Session Request and a Create SessionResponse are delivered between the S-GW and the L-GW to create a sessionfor the PDN connection.

In step S306, a session response message (i.e., the Create SessionResponse) is transmitted from the S-GW in response to the Create SessionRequest.

In step S307, the MME transmits a PDN Connectivity Accept (APN, PDNType, PDN Address, EPS Bearer Id, Session Management Request, ProtocolConfiguration Options) message to the eNodeB.

In step S308, the eNodeB transmits a radio resource control (RRC)connection reconfiguration message, which includes the PDN ConnectivityAccept. By performing steps S301 to S308, a PDN connection isestablished for a certain APN.

After a PDN connection is established, bearer resourceallocation/modification procedures may be performed. The UE may transmita BEARER RESOURCE ALLOCATION REQUEST message to the MME to request theallocation of bearer resources, or a BEARER RESOURCE MODIFICATIONREQUEST message to the MME to request the modification of bearerresources. The detailed features related to the BEARER RESOURCEALLOCATION REQUEST message are disclosed in Sections 6.5.3.2 to 6.5.3.4of 3GPP TS 24.301 V10.0.0 (2010-09) “Non-Access-Stratum (NAS) protocolfor Evolved Packet System (EPS); Stage 3(Release 10),” which areincorporated by reference in their entirety herein. Further, thedetailed features related to the BEARER RESOURCE MODIFICATION REQUESTmessage are disclosed in Sections 6.5.4.2 to 6.5.4.4 of 3GPP TS 24.301V10.0.0 (2010-09) “Non-Access-Stratum (NAS) protocol for Evolved PacketSystem (EPS); Stage 3(Release 10),” which e incorporated by reference intheir entirety herein.

If the bearer resource allocation request is rejected by the network,the MIME transmits BEARER RESOURCE ALLOCATION REJECT to the UE (S309).The BEARER RESOURCE ALLOCATION REJECT message includes an SM back-offtime value which is associated with a PDN connection which isestablished by steps S301 to S308. The BEARER RESOURCE ALLOCATION REJECTmessage further includes a cause code which indicates the reason why asession management (SM) request (i.e, BEARER RESOURCE ALLOCATIONREQUEST) is rejected.

A value of cause code included in the BEARER RESOURCEALLOCATION/MODIFICATION REJECT can be set to ‘26’ which indicatesinsufficient resource when the network reject the bearer resourceallocation/modification request.

Upon reception of the SM back-off time value in the session management(SM) reject message, the UE activates an SM back-off⁻timer according tothe received SM back-off time value (S310). In particular, if the APN isprovided in the rejected session management (SM) request message, the UEmay not initiate any session management procedures for the APN (e.g.,sending BEARER RESOURCE MODIFICATION REQUEST or BEARER RESOURCEALLOCATION REQUEST) while the SM back-off timer is running.

After the SM back-off time is activated, as discussed above, the networkmay request re-establishment of a PDN connection (S311) for performingSIPTO functions. For instance, the network may transmit a DEACTIVATE EPSBEARER CONTEXT REQUEST message with a cause code ‘39’ indicating‘reactivation requested’, thereby requesting to re-establish the PDNconnection of the UE. Upon receiving such a message, the UE performsdeactivation of the default EPS bearer context, stops the sessionmanagement (SM) back-off timer, if running, (S312) and therebyre-initiates a PDN connectivity request for the same APN as thedeactivated default EPS bearer context (S313). Since the UE stops thesession management (SM) back-off timer when the reactivation isrequested, the UE can further initiate session management (SM)procedures (i.e., transmitting PDN CONNECTIVITY REQUEST) for thecongested APN.

Alternatively, the features of FIG. 4 can be applied to handling the MMback-off timer. Namely, UE can stop the SM back-off timer, if running,of the affected PDN connection(s), and further stop the MM back-offtimer, if running, after receiving a DETACH REQUEST MESSAGE with adetach type indicating ‘re-attach required’.

Hereinafter, additional features related to re-activation/re-attachmentprocedures are further provided. If the re-activation/re-attachment isperformed by a UE in an idle state, the current 3GPP specificationrequires a low priority UE to identify itself as ‘delay tolerant’ in RRCestablishment cause. This may lead to a radio access network rejectingthe RRC connection of the UE for re-activation or re-attachment.

To solve the above-mentioned problem, the low priority UE may identifyitself as a normal priority UE (e.g. via RRC establishment cause) to theradio access network entity when initiating RRC connection forre-attachment or re-activation of the PDN connection.

Hereinafter, the second embodiment which is related to receiving apaging message while the MM back-off timer is running. The secondembodiment is also related to an idle mode signaling reduction (ISR)function, which allows the UE to remain simultaneous registered in anUTRAN/GERAN Routing Area (RA) and an E-UTRAN Tracking Area (TA) list.This allows the UE to make cell reselections between E-UTRAN andUTRAN/GERAN without a need to send additional TAU or RAU request, aslong as it remains within the registered RA and TA list. Consequently,the ISR function is one of features that reduce the mobility signalingand improve the battery life of UEs.

In the meantime, under the current 3GPP specification, when the networkpages the UE, the UE is required to perform the above-explained servicerequest procedure. However, this may lead to abnormal situations whichare as described in the followings, if the above-mentioned Tracking AreaUpdate (TAU) is not performed.

FIG. 5 is a flowchart illustrating a technical problem which may occurwhen the service request procedure is performed.

Referring to FIG. 5, in step S500, the ISR function is enabled withrespect to the UE. In particular, the ISR function can be enabled byreceiving a UE location registration accept message (e.g., TAU or RAUaccept message).

In step S505, the UE can transmit a request for activating a packet dataprotocol (PDP) context for a bearer ‘A’. Alternatively, the UE maytransmit a request for modifying a packet data protocol (PDP) context.After the request is transmitted to a 2G/3G network entity(e.g., ServingGPRS Support Node; SGSN), the bearer ‘A’ can be established, as shown instep S510. The PDP context used In 2G/3G network is corresponding to theabove-explained EPS bearers. In particular, the PDP context offers apacket data connection over which the UE and the network can exchange IPpackets. Usage of these packet data connections can be restricted tospecific services.

When using the ISR, the UE holds a TIN (Temporary Identity used in Nextupdate), which a parameter indicating which type of mobility managementcontext shall be used in the next signaling with the core network, whichcan be TAU (or RAU). Possible values of TIN include ‘GUTI’ (UE'sidentification known to the MME), ‘P-TMSI’ (UE's identification known tothe SGSN) and ‘RAT related TMSI’. For instance, in a situation where theTIN is set to ‘GUTI (Globally Unique Temporary Identity)’, the SGSN canfetch the UE's context from the MME by receiving a RAU request with theGUT1. While the GUTI is not a native identification to the SGSN, contextexchange can be performed by using the GUTI.

Under the current standard, UE's TIN is set to the P-TMSJ (packettemporary mobile subscriber identity) when the UE reselects to E-UTRAN(e.g. due to bearer configuration modifications performed onGERAN/UTRAN). In particular, when the PDP context is modified while LTEis in 2G or 3G and with ISR enabled, the UE can change its TIN to theP-TMSI in a certain situation to locally disable the TSR. Further, whenthe PDP context is activated and the UE moves from 2G (or 3G) network tothe E-UTRAN (i.e., LTE) while ISR is enabled, the UE can change its TINto the P-TMSI in a certain situation to locally disable the ISR.

If the UE moves to an area covered by the LTE system, it may disable theISR function locally and performs a TAU procedure. In particular, the UEtransmits a TAU request to the MME for updating TA (S515).

In step S520, if congestion occurs in the CN, an MM back-off time valuecan be included in a TAU reject which is transmitted in response to theTAU request. Upon receiving the MM back-off time value, an MM back-offtimer is initiated according to the received MM back-off time value. TheUE changes its state to EMM-REGISTERED.ATTEMPTING-TO-UPDATE.Alternatively, the MM back-off time value can be received before the UEmoves into the coverage of LTE, or during a TAU procedure.

Once the core network congestion is resolved (S530), the S-GW maytransmit DL data notification to the SGSN and the MME (S535). With theISR, the UE is registered to both systems, ITE and 2G/3G and paging willbe distributed to both. Namely, the UE receives a paging from the MME,as depicted in S540. For paging purposes, the mobile is paged with theS-TMSI. The S-TMSI can be constructed from the Mobility ManagementEntity Code (MMEC) and the M-TMSI (32-digit binary number that is partof the GUTI). The S-TMSI is a shorter format of GUTI and uniquelyidentifies the UE within an MME group. Further, the S-TMSI can be usedafter successful registration of a UE.

Under the current standard, when a paging with the S-TMSI is receivedwhile the MM back-off timer is running, the UE stops the MM back-offtimer. Further, in response to the paging with the S-TMSI, the UEperforms the above-explained service request procedure (S545). In thissituation, the MME does not have the UE's most up-to-date bearercontext, and thus the bearer ‘A’ may not be established. Eventually, theUE may locally disable the bearer ‘A’.

In sum, a new bearer/packet data protocol (PDP) context can beestablished when the UE in which the ISR is activated stays at 2G/3Gradio access network (S500-S510). If the UE moves to an area covered byLTE system, the UE disables ISR locally and performs the TAU (S515).Thereafter, the MME may reject the TAU request due to core networkcongestion with the MM back-off time value (S520-S525). After congestionis resolved, a paging can be transmitted to the UE, and the UE respondsto the paging with service request procedure (S530-545). In this case,the new bearer may not be established by the eNB when U-Plane bearersare setup, because MME does not have the UE's most up-to-date bearercontext (S550). Accordingly, the data cannot be delivered to the UE.

FIG. 6 is a flowchart illustrating a method of communicating data in awireless communication system including 2G/3G and LTE.

Referring to FIG. 6, a new bearer/packet data protocol (PDP) context canbe established when the UE in which the ISR is activated stays at 2G/3Gradio access network (S600-S10). If the UE moves to an area covered byLTE system, the UE disables ISR locally and performs the TAU (S615).Thereafter, the MME may reject the TAU request due to core networkcongestion with the MM back-off time value (S620-S625). After congestionis resolved, a paging can be transmitted to the UE, and the UE respondsto the paging with the TAU procedure (S630-645). In particular, the UEtransmit a TAU request in which the UE's TIN indicates the P-TMSI(S645). In this case, the new bearer may be established by the eNB whenU-Plane bearers are setup, because MME can have the UE's most up-to-datebearer context by fetching the UE's context from the SGSN. In sum, theexample of FIG. 6 allows the UE to perform the TAU procedure forresponding to the paging, instead, such that the MME would fetch theup-to-date bearer context from the SGSN and instruct the eNB to setup anew radio bearer for the incoming data.

In one design, it is preferred that the UE should perform the TAU/RAUinstead of service request procedure, with the active flag set, torespond to page, if the TAU/RAU is needed for the core network to updatethe UE context. If the page is due to a mobile terminated circuitswitched fallback (MT CSFB), an extended service request message is sentafter the completion of the TAU procedure.

Further, as explained above, under the current 3GPP specification, a lowpriority UE is required to use a “delay tolerant” in RRC establishmentcause, unless there is an emergency PDN connection, to initiate theTAU/RAU procedure from an idle state. This leads to the radio accessnetwork rejecting the RRC connection because the core network indicatingcongestion and RRC cause value indicating the UE as low priority.

Therefore, it is preferred that the low priority UE should identifyitself as a normal priority UE (e.g. via RRC establishment cause) to aradio access network entity when initiating the TAU/RAU procedure due toreceiving page.

Hereinafter, the third embodiment which is related to handling the MMback-off timer when performing inter-RAT handover.

FIG. 7 is a block diagram showing a wireless apparatus to implementtechnical features of this description. This may he a part of a UE, orcore network (CN) entity. The wireless apparatus 1000 may include aprocessor 1010, a memory 1020 and a radio frequency (RE) unit 1030.

The processor 1010 may be configured to implement proposed functions,procedures and/or methods described in this description. Layers of theradio interface protocol may be implemented in the processor 1010. Theprocessor 1010 may handle a MM or SM back-off timer. The memory 1020 isoperatively coupled with the processor 1010, and the RF unit 1030 isoperatively coupled with the processor 1010.

The processor 1010 may include application-specific integrated circuit(ASIC), other chipset, logic circuit and/or data processing device. Thememory 1020 may include read-only memory (ROM), random access memory(RAM), flash memory, memory card, storage medium and/or other storagedevice. The RF unit 1030 may include baseband circuitry to process radiofrequency signals. When the embodiments are implemented in software, thetechniques described herein can be implemented with modules (e.g.,procedures, functions, and so on) that perform the functions describedherein. The modules can be stored in the memory 1020 and executed by theprocessor 1010. The memory 1020 can be implemented within the processor1010 or external to the processor 1010 in which case those can becommunicatively coupled to the processor 1010 via various means as isknown in the art.

In view of the exemplary systems described herein, methodologies thatmay be implemented in accordance with the disclosed subject matter havebeen described with reference to several flow diagrams. While forpurposed of simplicity, the methodologies are shown and described as aseries of steps or blocks, it is to be understood and appreciated thatthe claimed subject matter is not limited by the order of the steps orblocks, as some steps may occur in different orders or concurrently withother steps from what is depicted and described herein. Moreover, oneskilled in the art would understand that the steps illustrated in theflow diagram are not exclusive and other steps may be included or one ormore of the steps in the example flow diagram may be deleted withoutaffecting the scope of the present disclosure.

What has been described above includes examples of the various aspects.It is, of course, not possible to describe every conceivable combinationof components or methodologies for purposes of describing the variousaspects, but one of ordinary skill in the art may recognize that manyfurther combinations and permutations are possible. Accordingly, thesubject specification is intended to embrace all such alternations,modifications and variations that fall within the scope of the appendedclaims.

What is claimed is:
 1. A method of processing data in a communicationsystem, the method comprising: establishing, by a user equipment (UE), adata connection associated with an access point name (APN); if the UEreceives a deactivate bearer context request message indicating thatreactivation is requested, stopping a session management back-off timerassociated with the established data connection if the sessionmanagement back-off timer is running, wherein the session managementback-off timer is a timer starting if a session management back-off timevalue is received at the UE, and wherein the session management back-offtime value is included in a reject message of a request for bearerresource modification or in a reject message of a request for bearerresource allocation; and re-initiating, by the UE, the data connectionassociated with the APN after stopping the session management back-offtimer.
 2. The method of claim 1, wherein the deactivate bearer contextrequest message includes a cause value set to ‘39’, which indicates thereactivation is requested.
 3. The method of claim 1, wherein the sessionmanagement back-off time value is included in a bearer resourcemodification reject message, and the UE does not transmit an additionalrequest for the bearer resource modification while the sessionmanagement back-off timer is running.
 4. The method of claim 3, whereinthe bearer resource modification reject message includes a cause valuewhich is set to ‘26’, which indicates ‘insufficient resources’.
 5. Themethod of claim 1, wherein the session management back-off time value isincluded in a bearer resource allocation reject message, and the UE doesnot transmit an additional request for the bearer resource allocationwhile the session management back-off timer is running.
 6. The method ofclaim 5, wherein the bearer resource allocation reject message includesa cause value which is set to ‘26’, which indicates ‘insufficientresources’.
 7. A user equipment (UE) in a communication system,comprising: a radio frequency unit; and a processor coupled to the radiofrequency unit and configured to: establish a data connection associatedwith an access point name (APN), if the UE receives a deactivate bearercontext request message indicating that reactivation is requested, stopa session management back-off timer associated with the established dataconnection if the session management back-off timer is running, whereinthe session management back-off timer is a timer starting if a sessionmanagement back-off time value is received at the UE, and wherein thesession management back-off time value is included in a reject messageof a request for bearer resource modification or in a reject message ofa request for bearer resource allocation, and re-initiate the dataconnection associated with the APN after stopping the session managementback-off timer.
 8. The user equipment of claim 7, wherein the deactivatebearer context request message includes a cause value set to ‘39’, whichindicates the reactivation is requested.
 9. The user equipment of claim7, wherein the session management back-off time value is included in abearer resource modification reject message, and the UE does nottransmit an additional request for the bearer resource modificationwhile the session management back-off timer is running.
 10. The userequipment of claim 9, wherein the bearer resource modification rejectmessage includes a cause value which is set to ‘26’, which indicates‘insufficient resources’.
 11. The user equipment of claim 7, wherein thesession management back-off time value is included in a bearer resourceallocation reject message, and the UE does not transmit an additionalrequest for the bearer resource allocation while the session managementback-off timer is running.
 12. The user equipment of claim 11, whereinthe bearer resource allocation reject message includes a cause valuewhich is set to ‘26’, which indicates ‘insufficient resources’.